Lab Report: Phytoplankton Under Ice

Adjunct Professor Donald Perovich was part of a team that discovered extensive blooms of phytoplankton under sea ice off the coast of Alaska. These tiny free-floating photosynthetic organisms comprise the base of the marine food web. The results were published in the journal Science in June.

Scientists previously thought there were few or no phytoplankton beneath sea ice because so little light could reach the water. Discovered during NASA’s ICESCAPE expedition to the Beaufort and Chukchi seas in 2010 and 2011, the under-ice blooms were concentrated enough to turn the water bright green. “It’s a pure discovery,” says Perovich, who studied the optical properties of the ice, “and now we have an entirely new ocean.”

The ice over the Chukchi Sea has shrunk from a 2- to 4-meter multi-year cover to a thin sheet that forms and melts each year. The thin ice and melt ponds transmit more light to the underlying ocean than do thick ice packs.

Perovich, a glaciologist at the U.S. Army Cold Regions Research and Engineering Laboratory in Hanover, and his Science article coauthors conclude: “Work is still required to determine the timing and spatial distribution of under-ice phytoplankton blooms across the Arctic Ocean, the extent to which they are controlled by thinning sea ice and proliferating melt pond fractions, and how they affect marine ecosystems. This is particularly important if we are to understand and predict the biological and biogeochemical impacts of ongoing and future changes in the Arctic Ocean physical environment.”